LETTER
Rhodium(I)-Catalyzed Synthesis of Aryltriethoxysilanes
807
Table 3 Hydrodediazoniation of Diazonium Tetrafluoroborate
Salts (continued)
(14) Dai, M. J.; Liang, B.; Wang, C. H.; Chen, J. H.; Yang, Z.
Org. Lett. 2004, 6, 221.
(15) Li, L.; Chen, H. B.; Lin, Y. B. Synth. Commun. 2007, 37,
985.
(16) Hubbard, A.; Okazaki, T.; Laali, K. K. J. Org. Chem. 2008,
73, 316.
(17) Simunek, P.; Bertolasi, V.; Lycka, A.; Machacek, V. Org.
Biomol. Chem. 2003, 18, 3250.
(18) Hanson, P.; Jones, J. R.; Taylor, A. B.; Walton, P. H.;
Timms, A. W. J. Chem. Soc., Perkin Trans. 2 2002, 1135.
(19) Darses, S.; Jeffery, T.; Genêt, J.-P.; Brayer, J.-L.; Demoute,
J.-P. Tetrahedron Lett. 1996, 37, 3857.
Entry Starting material
Product
Yield (%)
95a (89b)
BF4
N2
7
O2N
O2N
BF4
N2
8
9
93a
90b
91a
Cl
(20) Darses, S.; Michaud, G.; Genêt, J.-P. Eur. J. Org. Chem.
1999, 1875.
Cl
(21) Doyle, M. P.; Bryker, W. J. J. Org. Chem. 1979, 44, 1572.
(22) Filimonov, V. D.; Trusova, M.; Postnikov, P.;
Krasnokutskaya, E.; Lee, Y. M.; Hwang, H. Y.; Kim, H.;
Chi, K. Org. Lett. 2008, 10, 3961.
(23) Typical Method for the Preparation of Arenediazonium
Tosylate Salts
N2
BF4
F3C
BF4
N2
F3C
To a solution of methyl 4-aminobenzoate (1.0 mmol) in THF
(5 mL) and AcOH (5 mL) was added PTSA·H2O (1.1 mmol).
Immediately, pale solids were precipitated. About 8 mL of
AcOH was added until the solution turned clear again. The
solution was then cooled to –10 °C, and then t-BuONO (1.5
mmol) was added dropwise to the reaction. The mixture was
stirred for 30 min and then warmed to r.t. for another 30 min.
The clear solution was poured into Et2O (100 mL), and the
diazonium tosylate salt was precipitated. After careful
filtration, the product was collected to give a yield of 91%.
4-Methoxycarbonylbenzenediazonium Tosylate
IR (neat): 3566, 3483, 3101, 2311, 1723, 1438, 1302, 1195,
1122, 1036, 1009, 865, 817, 763, 684, 568, 525 cm–1. 1H
NMR (400 MHz, DMSO-d6): d = 2.27 (s, 3 H), 3.95 (s, 3 H),
7.09 (d, 2 H, J = 8.0 Hz), 7.46 (d, 2 H, J = 8.0 Hz), 8.39–8.43
(m, 2 H), 8.78–8.80 (m, 2 H) ppm. 13C NMR (100 MHz,
DMSO-d6): d = 20.86, 51.68, 115.41, 120.34, 125.59,
128.24, 131.47, 138.03, 145.30, 162.04, 166.13 ppm. MS
(ESI): m/z = 163 [M+], 162.9.
10
CF3
CF3
a Yields based on the GC-MS analysis.
b Isolated yields after silica gel column chromatography.
Supporting Information for this article is available online at
Acknowledgment
This work was financially supported by the National Natural Sci-
ence Foundation of China (No. 20602016), the 111 project, and the
Program for New Century Excellent Talents in University (NCET-
06-0904). We thank Mr. Yong Zhang and Mr. Ying Shuai Zhang for
GC measurements.
(24) Typical Procedure for the Silylation
Toluenediazonium tosylate salt (280 mg, 1.0 mmol, and
Bu4NI (369 mg, 1.0 mmol) were placed in a 25 mL of three-
necked flask which was capped with septum rubbers. The
flask was evacuated and backfilled with argon, and then
charged with DMF (4 mL), Et3N (3.0 mmol), and chloro(1,5-
cyclooctadiene) rhodium(I) dimer (5 mol%, 0.05 mmol).
The reaction mixture was stirred for 2 h at r.t.
Triethoxysilane (2.0 mmol) was added by a syringe through
the septum rubber. The reaction mixture was then stirred at
80–100 °C. After the reaction, the mixture was diluted with
Et2O, washed three times with H2O to remove DMF, and
dried over Na2SO4. The solvent was removed under reduced
pressure, and the residue was purified by Kugelrohr
distillation or silica gel column to give the desired
4-tolyltriethoxysilane 223 mg, yield 89%.
IR (neat): 2975, 2926, 2887, 1656, 1630, 1444, 1391, 1295,
1167, 1127, 1103, 1080, 959, 781, 712, 505 cm–1. 1H NMR
(400 MHz, CDCl3): d = 1.30 (t, 9 H, J = 7.2 Hz), 2.38 (s, 3
H), 3.91 (q, 6 H, J = 7.2 Hz), 7.23 (d, 2 H, J = 8.0 Hz), 7.63
(d, 2 H, J = 8.0 Hz) ppm. 13C NMR (100 MHz, CDCl3): d =
17.86, 21.20, 58.33, 127.81, 128.38, 134.59, 139.91 ppm.
MS (EI): m/z = 254 [M+], 254, 209, 195, 181, 162, 147, 139,
119, 91, 45.
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Synlett 2010, No. 5, 804–808 © Thieme Stuttgart · New York